1. Field of the Invention
The present invention relates to a circuit-forming charging powder and a multilayer wiring board using the same, especially to a circuit-forming charging powder (toner) to be used in printing a circuit pattern on an object by electrophotography, and a multilayer wiring board using the same.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. 4-236484 discloses a method for forming a desired circuit pattern on an insulating substrate by taking advantage of the electrostatic force used in conventional electrophotography, and a circuit-forming charging powder to be used in this wiring method. FIG. 1 shows a cross section of the conventional circuit-forming charging powder. The circuit-forming charging powder 100 with a mean particle size of 10 to 15 .mu.m assumes a structure in which a conductive metal powder 101 and a charge control agent 102 are uniformly dispersed in a heat-melt resin 103. The practical method for producing the circuit-forming charging powder 100 comprises the steps of: mixing a flake-shaped silver powder with a mean particle size of 0.4 .mu.m as a conductive metal powder 101, a metallic azo dye as a charge control agent 102 and a styrene-acrylic acid copolymer as a heat-melt resin 103 in a weight ratio of 80:1:19, respectively; and heat-melting the mixture followed by kneading with a kneader. Then, the mixture is roughly crushed with a cutter mill, finely crushed with a jet mill and classified with an air jet, thereby obtaining the circuit-forming charging powder 100.
However, the conventional circuit-forming charging powder involves a problem in that the circuit pattern can peel off the baked ceramic sheet when the powder is used for printing the circuit pattern on a ceramic green sheet by electrophotography because the ceramic green sheet shrinks during baking.